Final answer:
The Latin word for the ruler of the Empire is Imperator, which is translated as Kaiser in German and Tsar in Russian.
Step-by-step explanation:
The Latin word for the ruler of the Empire is Imperator. In German, this word is translated as Kaiser and in Russian, it is translated as Tsar. The imperial titles of the rulers of Russia and Germany, Tsar and Kaiser, are derived from the Latin word Imperator, which was the title of a victorious Roman general in the field.